Conventionally, there is a known capillary flow technique using capillary underfill (CUF) illustrated in FIGS. 17A to 17F as a flipchip mounting method. In the capillary flow technique, firstly flux is applied on a substrate terminal (FIG. 17A), and subsequently an IC chip provided with a solder ball is placed on the flux (FIG. 17B), followed by performing reflow soldering (FIG. 17C). After that, excess flux is cleaned (FIG. 17D) and the underfill is poured into a gap between the chip and the substrate utilizing a capillary phenomenon (FIG. 17E), and the underfill is thermoset by heat treatment (FIG. 17F).
However, in such capillary flow technique, use of flux, other than the underfill, is essential and also the steps of applying the flux (FIG. 17A) and cleaning the flux (FIG. 17D) have to be carried out, so that it was not possible to efficiently mount an IC chip. Particularly, in the cleaning step (FIG. 17D), it was sometimes not possible to wash away excess flux thoroughly.
With that, as a flipchip mounting method without using flux, there is a thermal compression bonding (TCB) technique using a preapplied underfill material (PAM) as illustrated in FIGS. 18A to 18C. In this technique, firstly, underfill of a preapplied type, such as non-conductive paste (NCP), for example, is applied on a substrate terminal (FIG. 18A), and subsequently, an IC chip provided with a solder ball is thermocompression bonded on the underfill (FIG. 18B). Due to the thermocompression bonding, the solder ball of the IC chip is melted and also the underfill is primarily cured. After that, the underfill is post cured by heat treatment (FIG. 18C).
Such thermal compression bonding technique takes not more than three steps, which are the step of applying underfill, the step of thermocompression bonding an IC chip and the step of heat treatment without using flux. Therefore, it is possible to efficiently mount an IC chip with the technique.
An example of the related technique may be found in JP H8-15119 A.